An external ventricular drain, also known as an extraventricular drain or
ventriculostomy, is a device used in neurosurgery that relieves elevated
intracranial pressure and hydrocephalus when the normal flow of cerebrospinal
fluid around the brain is obstructed. This is a plastic tube placed by
neurosurgeons, and managed by ICU nurses and Critical Care Paramedics to drain
fluid from the ventricles of the brain and thus keep them decompressed, as well
as to monitor intracranial pressure. Kocher's point
The tube is most frequently placed in Kocher's point with the goal of having
the catheter tip in the frontal horn of a lateral ventricle. The catheter is
normally inserted on the right side of the brain. An EVD is used to monitor
pressure in patients with brain injuries, intracranial bleeds or other
brain abnormalities that lead to increased fluid build-up. In draining
the ventricle it can also remove blood from the ventricular spaces. This is
important because blood is an irritant to brain tissue and can cause
complications such as vasospasm. Care of the Patient with an External
Ventricular Drain The external ventricular drain is
leveled to a common reference point, usually the tragus. The external
ventricular drain is set on a graduated burette the pressure level of the EVD is
prescribed by a healthcare professional, usually a neurosurgeon. Leveling the EVD
to a set pressure level is the basis for cerebrospinal fluid drainage;
hydrostatic pressure dictates CSF drainage. The fluid column pressure must
be greater than the weight of the CSF in the system before drainage occurs. It is
important that family members and visitors understand the patient's head
of bed position cannot be changed without assistance.
An example of a healthcare provider order regarding an EVD is: Level
external ventricular drain to 15 cmH20 above midbrain, open to drain
continuously, check and record cerebrospinal fluid drainage and
intracranial pressure every hour. The cerebral perfusion pressure can be
calculated from data obtained from the EVD and systemic blood pressure. In
order to calculate the CPP the intracranial pressure and mean arterial
pressure must be available. Complications
EVD is an invasive procedure. It is associated with several complications
categorised as below:- = Bleeding =
Commonly occurs along the EVD insertion tract or in the several layers of the
meninges that prohibit passage into the brain. If drilling or dural puncture is
not successful, you may dissect away dura and create a secondary bleed known
as an epidural or subdural hemorrhage. This situation can be life threatening,
and requires neurosurgical care. The most dreaded bleeding complication is
the realistic possibility of passing a catheter through a major aberrant vessel
or existing aneurysm. If this happens, the likelihood of death is significantly
increased, and may be immediate. The risk of hemorrhage is increased if the
patient is having coagulopathy. = Mechanical =
It can be sub-classified into:- Obstruction
Obstruction/occlusion of EVD commonly due to fibrinous/clot like material or
kinking of the tube. The brain can swell due to pressure build up in the
ventricles and permanent brain damage can occur. Physicians, nurses, and
Critical Care Paramedics often have to adjust or flush these small diameter
catheters to manage medical tube obstructions and occlusions at the
intensive-care bedside. Pressure settings are generally measured in
cmH2O. The equilibrium pressure of the EVD apparatus is adjusted based on
cerebrospinal fluid output, ICP waveform, imaging including CT or MRI of
the brain, and clinical response. Migration
During the EVD insertion, the EVD is tunneled subcutaneously and anchored
with suture. However, it is common for the EVD to dislodge or migrate. This
will cause the tip of the drain migrated away from its supposed position and
provides inaccurate ICP measurement or total occlusion of the drain.
Infection EVD is a foreign body inserted into
human body. It can serve as an object for bacterial attachment and cause
ascending infection. = Neurological =
Although not many neurological deficit has been reported, Chai et al. has
reported an association of patient's coma and his EVD malplacement. In his
report, the EVD was inserted too deep into the Fourth ventricle. The authors
hypothesised that the patient's coma was due to the EVD irritation to his
Recticular Activation System. The patient's consciousness improved after
the EVD was adjusted. See also
Subarachnoid Hemorrhage Critical Care Nursing
Neurocritical Care Neurointensive Care
References ^ a b "Care of the Patient Undergoing
Intracranial Pressure Monitoring/ External Ventricular Drainage or Lumbar
Drainage". AANN Clinical Practice Guideline Series. American Association
of Neuroscience Nurses. Retrieved 23 October 2012.
^ Kakarla UK, Kim LJ, Chang SW, Theodore N, Spetzler RF. "Safety and accuracy of
bedside external ventricular drain placement.". Neurosurgery 63: ONS162–6;
discussion ONS166–7. doi:10.1227/01.neu.0000335031.23521.d0.
PMID 18728595. ^ Chai FY, Farizal F, Jegan T. "Coma due
to malplaced external ventricular drain.". Turkish Neurosurgery 23:
561–563. doi:10.5137/1019-5149.JTN.5724-12.1.
PMID 24101284.